Suspension arrangement for cathode-ray tubes



Dec: 23, 1952 J. D. F. GREEN SUSPENSION ARRANGEMENT FOR CATHODE-RAY TUBES Filed Oct. '7, 1950 r o I. H e v n I 1/2621 Q F reen Attorney Patented Dec. 23, 1952 SUSPENSION ARRANGEMENT FOR CATHQDEERAY TUBES John Dudley Francis Green, Cambridge, England, assignor to Pye Limited, Cambridge, England,

a British company Application October 7, 1950, Serial No. 188,927

In Great Britain September 14,1949

3 Claims.

The present invention relates to a suspension arrangment for a cathode ray tube, which is particularly suitable for use in television apparatus. In television receivers as hitherto constructed, the neck end of the cathode ray tube is generally supported by a rubber grommet mounted in an aperture in a support bracket which may be directly carried by the chassis or alternatively from the focussing magnet. Examples of such arrangements are disclosed in specifications Nos. 2,440,403, 2,479,494, and application No. 73,347, filed January 28, 1949, all in the name of Donald Jackson. It will be clear that unless the neck of the cathode ray tube is located in the centre of the focussing magnet, then it becomes difficult to centre the beam correctly, and the present invention has for an object to provide an improved suspension arrangement which also serves for centering the neck of the tube within the magnet used for focussing.

According to the present invention, rubber or like resilient means for supporting the neck of a cathode ray tube is carried by an annular magnetic focussing device and extends through the focussing gap thereof to engage with the neck of the cathode ray tube passing through the central aperture of the focussingdevice'; 'With this construction the resilient suspension means may be easily centralised with respect to the magnetic focussing device which in turn results in the neck of the tube, when inserted through the focussing device, and supported by the resilient suspension means, being substantially centralised within the focussing device.

In one form of the invention, a ring of rubber or like material is mounted within an annular permanent focussing magnet and is formed with projections or ribs extending from its internal periphery so as to project through the focussing gap, said projections or ribs being adapted to engage the outer surface of the neck of the tube when'the latter is inserted through the bore of the focussing magnet. Preferably, however, the suspension means, instead of consisting of a complete ring, is formed as a number of pads, for example three pads, which are evenly spaced around the internal periphery of the bore of the magnet and are each provided with one or more protuberances forming projections or ribs. These pads are adapted .to be retained in position in the bore of the. magnet, for example by being elasticallywedged between the pole pieces of the complete .focussingdevice magnet. n

In order that the invention maybe more clearly understood, reference .willnow be made to vthe accompanying drawings, which illustrate the invention as applied to the focussing device describedin our co-pending application Serial No. 145,859, filed February 23, 1950, in the name of Patrick. Richard James Court, and in which Fig. 1 shows a side elevation of one embodiment according to the invention.

Fig. 2 shows a-rear elevation with one-half of the supporting bracket removed. 7

Fig. 3 shows a perspective view of the device with-abeam centering arrangement mounted thereon.

Fig. 4 is a longitudinal section of the device shown in Fig. 3.

Fig. 5 is a perspective view showing one ofthe rubber pads, and

Fig. 6 shows a front elevation partly in section, of a modified embodiment.

Referring to the drawings, an annular permanent magnet I is clamped between two end rings 2, 3- of Y magnetic material by longitudinally extending bolts 4, the internal peripheries of the endrings being fiangedor extended inwardly at 2a, 3a to form an annular focussing gap within the bore of the magnet;

One of the end rings 2 is made of such diameter that'its' outer periphery'extends beyond the outer periphery of: the annular permanent magnet I and: is formed at said oute periphery with inwardly'iand axially directed teeth 2b, preferably rectangular in shape.

The other ring 3 is of smaller diameter than the outer periphery of the permanent magnet l, and surrounding the external periphery of the end ring 3 is a further control ring member 5 of magnetic material, the internal diameter of which is approximately the same as the external diameter of the ring 3 whereby the control ring 5 is rotatable about the ring 3. The ring 5 is held in position surrounding the ring 3 by the pull of the magnet thereon, the ring 5 being'in magnetic contact with the magnet l. The external periphery of the control ring 5 is of approximately the same diameter of the end ring 2 and is formed at its external periphery with teeth 52), preferably substantially rectangular teeth, directed towards the teeth 2b projecting from the ring 2. Each of the rings 2, 3 and 5 may be made from sheet metal, the flanges 2a, 3a and the teeth 2b, 5b being formed by a suitable pressing operation.

As shown in the drawings, the ring 2 is formed with three rectangular teeth 2b, each extending for a distance of about one sixth of the periphery of the ring with gaps therebetween of similar length. Three similar rectangular teeth b are formed on the control ring 5, the gap between the two sets of teeth, when they lie opposite to one another, being less than the width of the focussing gap between the flanges 2a, 3a within the bore of the magnet. The gap between the teeth forms a magnetic path in shunt with the focussing gap, and by rotating the control ring 5 the teeth 5b carried thereby can be shifted from the position in which they lie opposite: the teeth 2b on the end ring 2 (position of maximum shunt) to a position in which they lie opposite to the gaps between the teeth 2b (position of minimum shunt). The flux in the inner focussing gap varies in accordance with the adjustment of the control ring and thus adjusts the focussing of the beam of the cathode ray tube. of which the neck 6 (Fig. 3) extends through. the bore of the focussing assembly. The adjustment may be effected by means of a lever of non-magnetic material secured by screws 8 to one of the teeth of the control ring.

Within the space defined by the internal periphery of the permanent magnet and the central flanges 2a, 3a of the end rings 2, 3 are disposed three pads l3 of rubber or like material each having a plurality of projections l4 extending from its inner surface and projecting through the focussing gap between the flanges 2a, 3a, the peaks of the projections l4 lying on a circle which is concentric with the said flanges and of a diameter corresponding to or slightly less than the diameter of the neck of the cathode ray tube. The projections |4 thus centralise the neck of the tube within the focussing device and allow for tolerance in the glass work. The tube may be easily withdrawn or replaced. Preferably the pad [3 is formed with inwardly tapered end walls l6 and has for the greater part of its height, a width slightly greater than the distance between the flanges 2a, 3a of the rings 2, 3 while the top of the side walls is bevelled as shown at I! (Fig. 5) so that due to the resilience of the rubber or the like, the pad when in position is held with its base resting against the bore of the magnet by the flanges 2a, 3a.

Preferably each of the pads is placed over one of the bolts 4, said bolt being accommodated in a transverse groove l8 provided in the base of the pad, whereby the pads are retained at the desired equal angular spacing within the bore of the magnet The pads l3 may be moulded and are preferably of such thickness as to support the tube when their backs are supported.

The focussing assembly may be carried from the chassis of the receiver by a bracket l0 clamped to the ring 3 by means of screws I passing through holes in a clamping ring l2 and threaded into threaded apertures in the ring 3. The bracket I0 is so shaped that when it is clamped between the ring l2 and the ring 3, it only bears firmly on the ring 3, clearance being allowed for free rotation of the control ring 5. With this method of mounting the focussing assembly, by loosening the clamping ring II, the complete magnet assembly can be rotated around the axis of the cathode ray tube to compensate for any irregularities in the field produced by the permanent magnet due either to its magnetisation or to slight variations in the position in which it is clamped by the screws 4 between the end rings 2 and 3. The complete assembly is locked in the desired adjusted position by tightening the screws In the perspective view of the device shown in Fig. 3 there is fltted to the front of the focussing assembly a device for centering the electron beam on th screen of the cathode ray tube.

This centering device comprises two annular permanent magnets 2|, 22 magnetised across their diameters. These magnets may be made of thin sheet metal and are mounted at the front of the focussing magnet so as to be rotatable around the axis of this magnet and thus around the axis of the neck of the cathode ray tube 6, extending through the centre of the assembly. Positioned between the focussing magnet and the magnet 2| are three annular spacers of sheet non-magnetic material 25, 26 and 21, between the two magnets 2| and 22 is a further annular spacer of sheet insulating non-magnetic material 28 and in front of the magnet 22 is another annular spacer of sheet non-magnetic material 29, the whole assembly being held in position to the front of the focus magnet by means of three clips 30 secured to the magnet by the screws 34. The longitudinally extending limbs 30a of these clips are positioned on a circle corresponding approximately to the internal diameter of the magnets 2| and 22 so that the latter are guidingly rotatable therearound. The internal diameters of the spacers are smaller than the internal diameter of the magnets 2| and 22, recesses 32 bein formed in the internal peripheries of the spacers to accommodate the clips 30 whereby rotation of the spacers is prevented. The whole assembly is held against the focus magnet by the outwardly turned ends 3% of the clips bearing on the outer surface of the spacer 29. The spacer 25 is of wavy or corrugated form so as to exert a slight axial pressure on the elements of the assembly and create friction between the magnets 2| and 22 and the adjacent spacers so that the magnets will remain in the adjusted position to which they are turned. To facilitate turning the magnets are provided with ears 2|a, 22a extending beyonds the external periphery of the spacers.

By making the centering assembly narrow in the axial direction it can be disposed between the focus magnet and the deflector coils.

Centering of the cathode ray beam is achieved by simply rotating the two annular magnets independently around the neck of the cathode ra tube. a

Fig. 6 shows a modified embodiment of the invention, in which the resilient means for supporting the neck of the cathode ray tube is constituted by a ring it of rubber or similarly resilient material, the outer periphery of which fits into and is seated in the bore of the annular permanent magnet I, while at its inner periphery the ring l9 has protuberances 20 which form projections or ribs extendin through the gap between the end ring portions 2a, 3a to support the neck of a cathode ray tube. The ring is preferably formed with transverse apertures or grooves 3| through which the bolts 4 extend.

Whilst two particular embodiments have been described it will be understood that various modifications may be made without departing from the scope of the invention.

I claim:

1. A focussing device for a cathode ray tube, comprising an annular permanent magnet, a pair of annular pole pieces respectively attached to the two ends of said mag-net and each having at its inner edge a collar-like portion extending into the central aperture of the magnet, to determine a focussing gap within said central aperture, a plurality of clamping screws extending through said pole pieces and through the central aperture of said magnet to clamp the pole members or pieces against said magnet, and a plurality of resilient rubber blocks placed against the wall of said central aperture of the annular magnet in angularly spaced relation to each other, each of said rubber blocks being formed with a, passage through which extends one of said clamping screws and with a shoulder engaging under said collar-like portions of the two pole pieces and having a supporting portion projecting through the focussing gap between said pole pieces, said supporting portion of each block being provided with a protuberance projecting inwardly of the magnet from the main surface of said supporting portion.

2. A focussing device for a cathode ray tube, comprising an annular permanent magnet, a pair of annular pole pieces respectively attached to the two ends of said magnet, said pole pieces each having their inner edge turned over to form collar-like portions facing each other to determine a focussing gap Within said central aperture, a plurality of clamping screws extending through said pole pieces and through the central aperture of said magnet to clamp the pole members or pieces against said magnet, and a plurality of resilient rubber blocks placed against the wall of said central aperture of the annular magnet in angularly spaced relation to each other, each of said rubber blocks having a body portion clamped between the two pole pieces and being formed with a recess across its base, which accommodates one of said clamping screws, and with a shoulder engaging under said collar-like portions of the two pole pieces and having a supporting portion projecting through the focussing gap between said pole pieces, said supporting portion being provided with two protuberances projecting inwardly of the magnet from the main surface of said supporting portion at the two sides respectively of said recess.

3. A focussing device for a cathode ray tube, comprising an annular permanent magnet, a pair of annular pole pieces respectively attached to the two ends of said magnet, said pole pieces each having their inner edge turned over to form collar-like portions facing each other to determine a focussing gap within said central aperture, and a plurality of resilient rubber blocks placed against the wall of said central aperture of the annular magnet in angularly spaced relation to each other, each of said rubber blocks having a body portion clamped between the two pole pieces and being formed with a shoulder engaging under said collar-like portions of the two pole pieces and having a supporting portion projecting through the focussing gap between said pole pieces, said supporting portion of each block being provided with two protuberances projecting inwardly of the magnet from the main surface of said supporting portion at two peripherally spaced points, the device further comprising a pair of annular pole-shunting members magnetically coupled respectively with two pole pieces and each having at least one axial projecting pole piece, one of said pole-shunting members being mounted for rotary adjustment about the axis of the mag-net whereby to move the projecting pole pieces of said shunting members into or out of alignment for adjusting the degree of magnetic shunt produced, and a pair of substantially annular plate members arranged at one end of the focussing device, said plate member being magnetised diametrically of, and rotatably adjustable about, the axis of the focussing device for adjusting the beam-centering effect of the focussing device.

JOHN DUDLEY FRANCIS GREEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,336,837 Bedford Dec. 14, 1943 2,416,687 Fry Mar. 4, 1947 2,455,676 Hillier Dec. 7, 1948 FOREIGN PATENTS Number Country Date 472,165 Great Britain Sept. 13, 1937 597,255 Great Britain Jan. 21, 1948 615.553 Great Britain Jan. 7, 1949 

